Problem this solves
Use these steps to calculate pulley diameters and groove counts so speed ratios and belt profiles stay correct.
Pulley sizing steps
- 1Confirm belt profile (SPA/SPB/SPC or timing).
- 2Count grooves and confirm belt quantity.
- 3Measure existing OD or pitch diameter.
- 4Calculate speed ratio: driver RPM / driven RPM.
- 5Select new pulley diameter based on ratio.
- 6Confirm bore type, taper series, and balance needs.
How to measure a pulley
Use calipers to measure OD across the rim. For timing pulleys, use pitch diameter when calculating ratios.
Pulley sizing worksheet
| Input | What it affects | Notes |
|---|---|---|
| Belt profile | Groove geometry | SPA/SPB/SPC or timing |
| Groove count | Belt capacity | Match existing drive |
| OD or pitch diameter | Speed ratio | Use pitch for timing belts |
| Bore type | Hub compatibility | Taper lock or pilot |
| RPM | Balance grade | High speed may require balance |
Send With Your Specification Request
- Belt profile and groove count
- OD or pitch diameter
- Bore size and taper series
- Keyway dimensions
- RPM and load details